Fluidic machining method and system

ABSTRACT

One exemplary embodiment of this disclosure relates to a method of forming an engine component. The method includes forming an engine component having an internal passageway, the internal passageway formed with an initial dimension. The method further includes establishing a flow of machining fluid within the internal passageway, the machining fluid changing the initial dimension.

BACKGROUND

Gas turbine engines typically include a compressor section, a combustorsection and a turbine section. During operation, air is pressurized inthe compressor section and is mixed with fuel and burned in thecombustor section to generate hot combustion gases. The hot combustiongases are communicated through the turbine section, which extractsenergy from the hot combustion gases to power the compressor section andother gas turbine engine loads.

Both the compressor and turbine sections may include alternating arraysof rotating blades and stationary vanes that extend into the core flowpath of the gas turbine engine. Engine components, such as turbineblades and vanes, are known to be cooled by routing a cooling fluidwithin one or more internal passageways.

In some examples, the internal passageways are in communication with aplurality of showerhead holes configured to create a showerhead film,which protects the component from the relatively hot gases flowingwithin the core flow path. The internal passageways may further beprovided in a serpentine shape, including a turn section betweenadjacent, parallel legs. Internal passageways may include turbulators,such as trip strips, for creating turbulence within the passageways,which increases cooling effectiveness.

SUMMARY

One exemplary embodiment of this disclosure relates to a method offorming an engine component. The method includes forming an enginecomponent having an internal passageway, the internal passageway formedwith an initial dimension. The method further includes establishing aflow of machining fluid within the internal passageway, the machiningfluid changing the initial dimension.

In a further embodiment of any of the above, the internal passageway isa serpentine-shaped passageway including a turn connecting two legs.

In a further embodiment of any of the above, the machining fluidenlarges a dimension of the turn.

In a further embodiment of any of the above, the machining fluidenlarges a dimension of the internal passageway.

In a further embodiment of any of the above, the internal passageway isin communication with a hole configured to communicate fluid from theinternal passageway to the exterior of the component.

In a further embodiment of any of the above, the machining fluid removesburrs adjacent the interface between the internal passageway and thehole, and enlarges a dimension of the hole adjacent the internalpassageway.

In a further embodiment of any of the above, the internal passagewayincludes at least one turbulator including a leading edge, the leadingedge initially being substantially normal to an expected flow pathwithin the internal passageway.

In a further embodiment of any of the above, the machining fluidpartially erodes the leading edge and provides the turbulator with asloped leading edge.

In a further embodiment of any of the above, the turbulator is one of atrip strip and a pedestal.

In a further embodiment of any of the above, the machining fluid isprovided with a Reynolds number substantially matching an expectedReynolds number of a flow of fluid within the internal passageway duringoperation of an engine.

In a further embodiment of any of the above, the machining fluid isconfigured to partially erode a material of the engine component, andincludes one of (1) a chemical solvent and (2) a suspended grit media.

In a further embodiment of any of the above, the method includes formingthe engine component using one of an additive manufacturing technique, aforging process, and a casting process before introducing the machiningfluid into the internal passageway.

In a further embodiment of any of the above, the engine componentincludes a plurality of internal passageways, and wherein a flow ofmachining fluid is established within each of the internal passageways.

In a further embodiment of any of the above, the machining fluid isprovided in the internal passageway for a predetermined time.

Another exemplary embodiment of this disclosure relates to a system formachining an engine component. The system includes an engine componentincluding an internal passageway, the internal passageway formed with aninitial dimension. The system further includes a source of machiningfluid, the source of machining fluid in communication with the internalpassageway, and a control. Further, a flow of machining fluid isestablished within the internal passageway in response to an instructionfrom the control, the machining fluid configured to change the initialdimension.

In a further embodiment of any of the above, the internal passageway isa serpentine-shaped passageway including a first leg, a second leg, anda turn connecting the first and second legs, and wherein the machiningfluid enlarges a dimension of the turn and a dimension of the secondleg.

In a further embodiment of any of the above, the internal passageway isin communication with a hole configured to communicate fluid from theinternal passageway to the exterior of the component, and wherein themachining fluid enlarges a dimension of the hole adjacent the internalpassageway.

In a further embodiment of any of the above, the internal passagewayincludes at least one turbulator initially including a leading edgesubstantially normal to an expected flow path within the internalpassageway, and wherein the machining fluid provides the turbulator witha curved leading edge.

In a further embodiment of any of the above, the turbulator is one of atrip strip and a pedestal.

In a further embodiment of any of the above, the engine component is oneof a rotor blade, a stator vane, and a blade outer air seal (BOAS).

The embodiments, examples and alternatives of the preceding paragraphs,the claims, or the following description and drawings, including any oftheir various aspects or respective individual features, may be takenindependently or in any combination. Features described in connectionwith one embodiment are applicable to all embodiments, unless suchfeatures are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings can be briefly described as follows:

FIG. 1 schematically illustrates an example gas turbine engine.

FIG. 2 illustrates an example system.

FIG. 3A illustrates an example internal passageway including twoturbulators.

FIG. 3B illustrates the internal passageway of FIG. 3A following fluidicmachining.

FIG. 4A illustrates an example film hole entrance.

FIG. 4B illustrates the film hole entrance of FIG. 4A following fluidicmachining.

FIG. 5A illustrates an internal passageway including a serpentine turn.

FIG. 5B illustrates the internal passageway of FIG. 5A following fluidicmachining.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flow path B in abypass duct defined within a nacelle 15, while the compressor section 24drives air along a core flow path C for compression and communicationinto the combustor section 26 then expansion through the turbine section28. Although depicted as a two-spool turbofan gas turbine engine in thedisclosed non-limiting embodiment, it should be understood that theconcepts described herein are not limited to use with two-spoolturbofans as the teachings may be applied to other types of turbineengines including three-spool architectures.

The exemplary engine 20 generally includes a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis A relative to an engine static structure 36 viaseveral bearing systems 38. It should be understood that various bearingsystems 38 at various locations may alternatively or additionally beprovided, and the location of bearing systems 38 may be varied asappropriate to the application.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a first (or low) pressure compressor 44 and afirst (or low) pressure turbine 46. The inner shaft 40 is connected tothe fan 42 through a speed change mechanism, which in exemplary gasturbine engine 20 is illustrated as a geared architecture 48 to drivethe fan 42 at a lower speed than the low speed spool 30. The high speedspool 32 includes an outer shaft 50 that interconnects a second (orhigh) pressure compressor 52 and a second (or high) pressure turbine 54.A combustor 56 is arranged in exemplary gas turbine 20 between the highpressure compressor 52 and the high pressure turbine 54. A mid-turbineframe 57 of the engine static structure 36 is arranged generally betweenthe high pressure turbine 54 and the low pressure turbine 46. Themid-turbine frame 57 further supports bearing systems 38 in the turbinesection 28. The inner shaft 40 and the outer shaft 50 are concentric androtate via bearing systems 38 about the engine central longitudinal axisA which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The mid-turbine frame 57 includes airfoils 59 whichare in the core airflow path C. The turbines 46, 54 rotationally drivethe respective low speed spool 30 and high speed spool 32 in response tothe expansion. It will be appreciated that each of the positions of thefan section 22, compressor section 24, combustor section 26, turbinesection 28, and fan drive gear system 48 may be varied. For example,gear system 48 may be located aft of combustor section 26 or even aft ofturbine section 28, and fan section 22 may be positioned forward or aftof the location of gear system 48.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than about ten (10), thegeared architecture 48 is an epicyclic gear train, such as a planetarygear system or other gear system, with a gear reduction ratio of greaterthan about 2.3 and the low pressure turbine 46 has a pressure ratio thatis greater than about five. In one disclosed embodiment, the engine 20bypass ratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout five 5:1. Low pressure turbine 46 pressure ratio is pressuremeasured prior to inlet of low pressure turbine 46 as related to thepressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. The geared architecture 48 may be an epicycle geartrain, such as a planetary gear system or other gear system, with a gearreduction ratio of greater than about 2.3:1. It should be understood,however, that the above parameters are only exemplary of one embodimentof a geared architecture engine and that the present invention isapplicable to other gas turbine engines including direct driveturbofans.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, withthe engine at its best fuel consumption—also known as “bucket cruiseThrust Specific Fuel Consumption (‘TSFC’)”—is the industry standardparameter of lbm of fuel being burned divided by lbf of thrust theengine produces at that minimum point. “Low fan pressure ratio” is thepressure ratio across the fan blade alone, without a Fan Exit Guide Vane(“FEGV”) system. The low fan pressure ratio as disclosed hereinaccording to one non-limiting embodiment is less than about 1.45. “Lowcorrected fan tip speed” is the actual fan tip speed in ft/sec dividedby an industry standard temperature correction of [(Tram ° R)/(518.7°R)]^(0.5). The “Low corrected fan tip speed” as disclosed hereinaccording to one non-limiting embodiment is less than about 1150ft/second.

FIG. 2 illustrates an example engine component 60 arranged relative to amachining system 95. In this example, the engine component 60 is a rotorblade of the engine 20. This disclosure is not limited to rotor blades,however, and extends to other engine components such as stator vanes,blade outer air seals (BOAS), and others. Further, this disclosure maybe applicable outside the context of engine components, and may extendto the engine 20 itself, or components that are not used in an engine.

In one example, the engine component 60 is provided in a high pressureturbine 54 of the engine 20. This disclosure is not limited tocomponents located within the high pressure turbine 54, however, andextends to components in other sections of the engine 20.

The component 60 in this example includes a root 62, a platform 64, andan airfoil section 66 extending in the radial direction Z, which isgenerally normal to the engine central longitudinal axis A. The airfoilsection 66 terminates at a tip 68. The airfoil section 66 furtherincludes pressure and suction side walls 70, 72 extending between aleading edge 74 and a trailing edge 76. The airfoil section 66 may bedirectly exposed to relatively hot gases within the core flow path Cduring operation of the engine 20. Accordingly, the component 60 mayinclude one or more cooling features, as will be discussed below.

In the illustrated example, the component 60 includes a plurality ofinternal passageways for directing a flow of cooling fluid within theairfoil section 66 during engine operation. The component 60, in thisexample, includes a leading edge passageway 78, a serpentine passageway80, and a trailing edge passageway 82. Each of the passageways 78, 80,82, may include a plurality of turbulators, such as pedestals, angledtrip strips 84 or chevron-shaped trip strips 86. Other trip strip shapescome within the scope of this disclosure.

The leading edge passageway 78 is in fluid communication with aplurality of showerhead holes 88. The showerhead holes 88 are configuredto direct a flow of fluid from the leading edge passageway 78 to theexterior of the airfoil section 66 to create a film of cooling fluidadjacent the leading edge 74 of the component 60.

The serpentine passageway 80 includes a first leg 90 extending in theradial direction Z, and a turn 92 adjacent the tip 68 of the airfoilsection. The turn 92 essentially turns a flow of fluid from the firstleg 90 to a second leg 94, which is generally parallel to the first leg90.

The trailing edge passageway 82 runs parallel to the first and secondlegs 90, 94, and is configured to direct a flow of fluid along thetrailing edge 76. In this example, the fluid exits the airfoil section66 at the trailing edge 76. The trailing edge passageway 82 may be fedfrom the second leg 94, or may be provided with a flow of cooling fluidfrom another source.

The engine component 60 may be initially formed, in one example, byusing a casting technique, such as investment casting. The enginecomponent 60 may be formed using other techniques, such as forging,additive manufacturing, etc. This disclosure may be particularlybeneficial in the context of additive manufacturing, where partiallyfused particles may need to be cleaned before being used in an engine.

In one example of this disclosure, the internal passages of the enginecomponent 60 are machined following initial forming (e.g., casting,forming, additive manufacturing) by establishing a flow of a machiningfluid F within the internal passages. The machining fluid F isconfigured to flow through the internal passageways 78, 80, 82 for aspecified, predetermined time to partially erode (e.g., etch, grind) theinternal passages, and in particular to change an initial dimension(e.g., a dimension provided from the initial forming process) of theinternal passageways 78, 80, 82.

As illustrated in FIG. 2, the engine component 60 may be arrangedrelative to a machining system 95 including a source of machining fluid96, a control 97, and one or more pumps, valves, and conduits forrouting the machining fluid F relative to the component 60. The control97 is configured to send instructions to selectively establish a flow ofmachining fluid F within the component 60.

The machining fluid F may be any known type of machining fluid.Generally, machining fluid F is configured to machine surfaces that aresubstantially normal to a flow path of the machining fluid F. In oneexample, the machining fluid F includes a chemical solvent (e.g., anacid or a base). The solvent is configured to erode certain materials,such as metals and ceramics. In another example, the fluid F may includea grit media suspended within a base fluid (such as water or air). Thegrit media is configured to essentially grind or etch material as itflows over that material.

A flow of the machining fluid F is provided within the engine component60 for a predetermined amount of time. The amount of time machines theinternal passageways to enhance cooling without damaging the enginecomponent 60. The amount of time may be determined based on a model,trial and error, or both.

Further, during machining, it may be important in some examples to matchthe Reynolds number of the expected cooling flow with the machiningfluid F. Doing so simulates the expected operating conditions of theengine component 60, which increases the effectiveness of the fluidicmachining process.

With reference to FIG. 3A, an example passageway 98 of the enginecomponent 60 is illustrated. The passageway 98 is representative of anyof the passageways 78, 80, 82. In this example, the passageway 98includes opposed walls 100, 102, each including a respective trip strip104, 106 projecting into the passageway 98 and toward the opposite wall100, 102.

After the passageway is initially formed (e.g., following casting), eachof the trip strips 104, 106 extends a first distance D₁ along the lengthof the passageway 98, and extends a second distance D₂ from a respectivewall 100, 102 into the passageway 98. In this example, the trip strips104, 106 initially have a rectangular shape (having a length D₁, and aheight D₂) in cross-section. Additionally, the trip strips 104, 106 eachinclude a leading edge 104L, 106L substantially normal to a respectivewall 100, 102.

As illustrated in FIG. 3A, a flow of machining fluid F is introducedinto the passageway 98 for a predetermined time. As mentioned above, themachining fluid F is configured to interact with surfaces that aresubstantially normal to the flow of machining fluid F. Accordingly, themachining fluid F changes the outer contour and overall dimensions ofthe trip strips 104, 106.

In particular, the machining fluid F essentially rounds the edges of thetrip strips 104, 106, and provides the trip strips with a substantiallysloped, arcuate contour 104S, 106S, as illustrated in FIG. 3B. Theinitial contour of the trip strips 104, 106 is shown in phantom in FIG.3B. Additionally, the height of the trip strips 104, 106 may be reducedfrom D₂ to D₃. The length D₁ of the trip strips 104, 106 is also notuniform along the height of the trip strips. That is, a first chord C₁adjacent a base 104B, 106B of the trip strips 104, 106 is larger than asecond chord C₂ adjacent the top of the trip strips 104T, 106T.

The sloped contour 104S, 106S of the trip strips 104, 106 (FIG. 3B) ismore aerodynamic and less likely to create stagnation than thesubstantially normal leading edges 104L, 106L (FIG. 3A). Further, thesloped contour enhances the ability of the trip strips 104, 106 tocreate vortices within a flow of cooling fluid, and therefore increasescooling effectiveness.

FIGS. 4A-4B illustrate the above-discussed concept in the context of theleading edge passageway 78 and the showerhead holes 88. In someexamples, the engine component 60 is not initially formed with theshowerhead holes 88 having a diameter O₁. Accordingly, the showerheadholes 88 may be formed by a drilling process, for example. This processmay leave excess material (e.g., burrs) 108, 110 at the intersectionbetween the leading edge passageway 78 and the showerhead hole 88. Thereotherwise may be sharp corners 112, 114 between the leading edgepassageway 78 and the showerhead holes 88.

The machining fluid F is provided along the leading edge passageway 78and erodes the excess material 108, 110 and the sharp corners 112, 114to provide an essentially smooth, aerodynamic contour, illustrated at116, 118 between the leading edge passageway 78 and the showerhead hole88. The machining fluid F further increases the diameter of theshowerhead hole 88 adjacent the leading edge passageway 78 from O₁ toO₂. This increases the ability of fluid to enter the showerhead holes 88and reduces stagnation (which, in turn, enhances cooling).

FIGS. 5A-5B illustrate a serpentine passageway 80. In this example, aturn 92 is bounded in the radial direction Z by a radially outer wall120. After initial forming, the turn 92 includes a first height H₁.Cooling fluid may become stagnant at a potential stagnation point 122between the outer wall 120 of the turn 92 and an outer wall 124 of thesecond leg 94. After initial forming, the second leg 94 includes a firstwidth W₁.

As illustrated in FIG. 5B, the machining fluid F partially erodes theouter wall 120, increasing the height of the turn 92 from H₁ to H₂, andprovides the outer wall 120 with a substantially arcuate, roundedcontour. The machining fluid F further erodes the second leg 94,increasing the width of the second leg 94 from W₁ to W₂ by machininginto both the outer wall 122 and the inner wall 126 of the second leg94. These increased dimensions H₂, W₂ adjacent the potential stagnationpoint 122 increase the ability of cooling flow to make the turn betweenthe legs 90, 94.

While FIGS. 3A-5B illustrate three examples where fluidic optimizationis beneficial, it should be understood that this disclosure is notlimited to use in a particular portion of the engine component. That isthis disclosure extends to other internal passageways that may requireinternal optimization.

Although the different examples have the specific components shown inthe illustrations, embodiments of this disclosure are not limited tothose particular combinations. It is possible to use some of thecomponents or features from one of the examples in combination withfeatures or components from another one of the examples.

One of ordinary skill in this art would understand that theabove-described embodiments are exemplary and non-limiting. That is,modifications of this disclosure would come within the scope of theclaims. Accordingly, the following claims should be studied to determinetheir true scope and content.

What is claimed is:
 1. A method of forming an engine component,comprising: forming an engine component having an internal passageway,the internal passageway formed with an initial dimension; andestablishing a flow of machining fluid within the internal passageway,the machining fluid changing the initial dimension, wherein the internalpassageway includes at least one turbulator including a leading edge,the leading edge initially being substantially normal to an expectedflow path within the internal passageway, wherein the machining fluidpartially erodes the leading edge and provides the turbulator with asloped leading edge, wherein the flow of machining fluid exhibits aReynolds number substantially matching an expected Reynolds number of aflow of cooling fluid within the internal passageway during operation ofan engine.
 2. The method as recited in claim 1, wherein the internalpassageway is a serpentine-shaped passageway including a turn connectingtwo legs.
 3. The method as recited in claim 2, wherein the machiningfluid enlarges a dimension of the turn.
 4. The method as recited inclaim 3, wherein the machining fluid enlarges a dimension of theinternal passageway.
 5. The method as recited in claim 1, wherein theinternal passageway is in communication with a hole configured tocommunicate fluid from the internal passageway to the exterior of thecomponent.
 6. The method as recited in claim 5, wherein the machiningfluid removes burrs adjacent the interface between the internalpassageway and the hole, and enlarges a dimension of the hole adjacentthe internal passageway.
 7. The method as recited in claim 1, whereinthe turbulator is one of a trip strip and a pedestal.
 8. The method asrecited in claim 1, wherein the machining fluid is configured topartially erode a material of the engine component, and includes one of(1) a chemical solvent and (2) a suspended grit media.
 9. The method asrecited in claim 1, including forming the engine component using one ofan additive manufacturing technique, a forging process, and a castingprocess before introducing the machining fluid into the internalpassageway.
 10. The method as recited in claim 1, wherein the enginecomponent includes a plurality of internal passageways, and wherein aflow of machining fluid is established within each of the internalpassageways.
 11. The method as recited in claim 1, wherein the machiningfluid is provided in the internal passageway for a predetermined time.12. A method of forming an engine component, comprising: forming anengine component having an internal passageway, the internal passagewayformed with an initial dimension, wherein the internal passagewayincludes at least one turbulator including a leading edge, the leadingedge initially being substantially normal to an expected flow pathwithin the internal passageway; and establishing a flow of machiningfluid within the internal passageway, the machining fluid changing theinitial dimension, wherein the machining fluid partially eroding theleading edge and providing the turbulator with a sloped leading edge,and wherein the flow of machining fluid exhibits a Reynolds numbersubstantially matching an expected Reynolds number of a flow of coolingfluid within the internal passageway during operation of an engine.